This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We developed tomographic phase microscopy (TPM) capable of measuring refractive index of a live cell with high resolution. Three dimensional imaging of a live cell provides a way to investigate optical properties of individual organelles. In this project, we have developed new algorithm based on the diffractive nature of light. With the help of new algorithm, we can clearly resolve detailed structures in the out-of focus plane which has not been resolved with current tomography technique. This algorithm makes it possible to obtain high resolution 3D images for a much thicker sample than the depth of focus of imaging system.